AD8610: Short circuit current - driving the AD7667

Document created by analog-archivist Employee on Feb 23, 2016
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Does the output buffer of AD8610 opamp has short current limitting circuits?
What its characteristics?
Can the AD8610 drive AD7667 ADC?


AD8610 does have short circuit protection, limiting the current to typically
65-100mA. The absolute maximum ratings state that the device can withstand an
output short circuit to GND for an unlimited time.

The type of current limiting seems to be progressive rather than "foldback"
current limiting. See figure 24 in the datasheet.

The AD7667 datasheet recommends the AD8610 for low-frequency applications. This
can be explained as follows.

- The AD8610s settling time to 0.01% is typically 750ns. This is not sufficient
to drive the AD7667 at 1MHz maximum sampling rate with an input signal
frequency of 500kHz, since the acquisition time is only 250ns in this case. If
the acquisition time is >750ns or if the signal does not swing full scale
between samples (i.e. lower signal frequency) then the AD8610 will provide
excellent performance

- The AD8610s low noise makes it suitable for driving 16 bit converters

- The AD8610s short circuit current of 65-100mA is approaching the limit of
what the AD7667's input protection diodes can safely accommodate. However, you
would normally place a small resistor in series with the input, to assist with
antialiasing filtering and this will have a second benefit of reducing the
AD8610 current if the AD8610 saturates and goes outside the AD7667's supply
voltage range.